Passing variables by reference

PhreaK wrote: »

Within netlinx is it possible to pass a variable by reference? If so, how?

From the help file:

The NetLinx compiler passes all variables by reference. This means that the variable the subroutine operates on is the same variable the caller passed. Any change made to a variable passed as a calling parameter updates the value of the variable from the perspective of the caller. You can take advantage of this pass by reference feature to return an updated value through a calling parameter rather than as the return value.

Constants, on the other hand, are passed by value. When this happens, a copy of the parameter is delivered to the subroutine. Any change made to the variable representing the constant is lost once the function or subroutine finishes.

Paul

There are other tricks that allow you to pass a variable by value.

STACK_VAR CHAR sHaystack[20];
STACK_VAR CHAR sNeedle[20];

// pass by reference
sHaystack = 'TRANSPORT=1:PLAY';
sNeedle = REMOVE_STRING([COLOR=red]sHaystack[/COLOR],'=',1);
// sHaystack = '1:PLAY'
// sNeedle = 'TRANSPORT='

// pass by value
sHaystack = 'TRANSPORT=1:PLAY';
sNeedle = REMOVE_STRING([COLOR=red]"sHaystack"[/COLOR],'=',1);
// sHaystack = 'TRANSPORT=1:PLAY'
// sNeedle = 'TRANSPORT='

PhreaK wrote: »

It must be time for another coffee.

You mean you haven't got a caffeine drip yet? How do programmers ever expect to get the job done without the right tools. Maybe start out with caffeine tablets to get into it and then move on to the harder options...

mpullin wrote: »

There are other tricks that allow you to pass a variable by value.

STACK_VAR CHAR sHaystack[20];
STACK_VAR CHAR sNeedle[20];

// pass by reference
sHaystack = 'TRANSPORT=1:PLAY';
sNeedle = REMOVE_STRING([COLOR=red]sHaystack[/COLOR],'=',1);
// sHaystack = '1:PLAY'
// sNeedle = 'TRANSPORT='

// pass by value
sHaystack = 'TRANSPORT=1:PLAY';
sNeedle = REMOVE_STRING([COLOR=red]"sHaystack"[/COLOR],'=',1);
// sHaystack = 'TRANSPORT=1:PLAY'
// sNeedle = 'TRANSPORT='

Why would you ever do this? I can't think of any reason why I would ever want to pass a string by value when it can be passed by reference. It just opens up a can of bugs.
Paul